Smoke and dirt rise from the city of Severodonetsk, during shelling in the eastern Ukrainian region of Donbas, May 26, 2022. AFP
Russia created a corridor to evacuate civilians from the Azot chemical factory, but "the Kyiv authorities cynically scuppered the humanitarian operation", the Russian defence ministry said in a statement.
On Tuesday, Russia said it would set up a humanitarian corridor between 0500 GMT and 1700 GMT to allow civilians in the Azot plant to leave Severodonetsk for territories in the Lugansk region held by pro-Moscow separatists.
But the defence ministry accused Ukrainian forces of violating the ceasefire "on several occasions" and using the humanitarian operation to redeploy its troops in more favourable fighting positions.
It was impossible to verify the claims independently.
The Ukrainian authorities have said hundreds of civilians have taken refuge in the Azot plant and that the factory is constantly bombarded.
The situation there is reminiscent of the sprawling Azovstal steelworks in the southeastern port city of Mariupol, where civilians and fighters resisted a weeks-long Russian siege before being defeated.
Russia announced multiple ceasefires during the siege to evacuate civilians through humanitarian corridors, but many were unsuccessful as Moscow and Kyiv accused each other of reneging on their word.
Intense fighting for the strategic city of Severodonetsk in eastern Ukraine has raged for weeks as Russia advances in the eastern Donbas region.
Capturing Severodonetsk, the largest city in Lugansk still under Ukrainian control, would allow Moscow's forces to advance on Sloviansk and Kramatorsk further west.